The present invention, in some embodiments thereof, relates to siRNAs capable of down-regulating CD24 and to uses thereof for the treatment of a variety of diseases including cancer.
Cell adhesion proteins are dynamic molecules involved in several aspects of cellular function including migration, inflammation and tissue development. For example, the maturation of hematopoietic cells is associated with the regulated expression of numerous genes, some of which encode cell surface proteins that mediate maturation-stage-specific signals into and out of the cell. This is accomplished by binding of the cell surface protein to a variety of ligands such as soluble interleukins and adhesion receptors either on other cells or within the extracellular matrix. One such cell adhesion molecule found in most cells of hematopoietic lineages is CD24, a glycoprotein consisting of 31 to 35 amino acid residues anchored to the plasma membrane by glycosyl phosphatidylinositol [Kay et al., J. Immunol., 1991, 147, 1412-1416]. The apparent molecular weight of CD24 ranges between 32 KDa in brain and 70 KDa in lymphoid cells due to variable glycosylation patterns. In non-malignant cells CD24 is primarily found in developing (immature but not mature) B-cells and neurons. It has also been detected in cells having a malignant phenotype including neuroblastoma cells [Kadmon et al., Biochem. Biophys. Res. Commun., 1995, 214, 94-101] and malignant brain cells [Poncet et al., Acta. Neuropathol., 1996, 91, 400-408].
The human CD24 gene was cloned by Kay, Rosten and Humphries [Kay et al., J. Immunol., 1991, 147, 1412-1416] and is also disclosed and claimed in PCT publication WO 99/41376 [Yang et al., 1999].
Human CD24 is located on chromosome 6 at band q21. The chromosome region 6q16-q22 has been shown to be associated with recurrent chromosome abnormalities in lymphoproliferative and myeloproliferative diseases [Sandberg, Chromosomes in Human Cancer and Leukemia 2nd ed., 1990, Elsevier: New York, 625-751]. Additional homologous sequences of CD24 have been mapped to chromosomes 15q21-q22 and Yq11. CD24 is thus a member of a multigene family but it is not known yet known if the genes related to CD24 are functional (Hough et al., Genomics, 1994, 22, 154-161). Pass et al have shown that the 5′-flanking sequence of CD24 has cell-type-specific activity resulting in enhancement of expression of CD24 (relative to a control promotor) in small cell lung cancer cell lines [Pass et al., Int. J. Cancer, 1998, 78, 496-502].
The principal cellular function of human CD24 is not clear but several B cell-related functions have been suggested. CD24 is involved in B cell adhesion both directly and by modifying the specificity and/or avidity of other adhesive interactions such as the interactions between VLA-4 and VCAM-1, VLA-4 and fibronectin [Hahne et al., J. Exp. Med., 1994, 179, 1391-1395] and the interaction of VLA-5 with L1 [Ruppert et al., J. Cell Biol., 1995, 131, 1881-1891]. The investigations of Zarn et al. indicate an involvement of CD24 in the signaling processes of kinases c-fgr in small cell lung cancer and with kinase lyn in erythroleukemia [Zarn et al., Biochem. Biophys. Res. Commun., 1996, 225, 384-391].
Studies of the interactions of CD24 with P-selectin in a breast cancer carcinoma cell line indicate that CD24 may play a role in mediating an adhesion pathway in cancer metastasis [Aigner et al., Faseb. J., 1998, 12, 1241-1251].
In a rat glioma cell line, it was found that CD24 stimulates the migration of gliomas. This suggests a role for CD24 in promotion of brain invasion by human gliomas [Senner et al., J. Neuropathol. Exp. Neurol., 1999, 58, 795-802].
Anti-CD24 antibodies (in some cases including immunotoxins) have been used to inhibit CD24 in investigative and therapeutic efforts to control various diseases including: Epstein-Barr virus-induced B-lymphoproliferative disorder, [Benkerrou et al., Blood, 1998, 92, 3137-3147; Fischer et al., N. Engl. J. Med., 1991, 324, 1451-1456; Lazarovits et al., Clin. Invest. Med., 1994, 17, 621-625], small cell lung cancer [Jackson et al., Cancer Res., 1992, 52, 5264-5270; Zangemeister-Wittke et al., Int. J. Cancer, 1993, 53, 521-528; Zarn et al., Biochem. Biophys. Res. Commun., 1996, 225, 384-39] and Burkitt's lymphoma [Schnell et al., Int. J. Cancer, 1996, 66, 526-531].
U.S. Pat. Appl. 20040097448 teaches therapeutic strategies aimed at inhibiting the action of CD24 by administering anti sense oligonucleotides targeted to nucleic acid encoding CD24 for the treatment of small cell lung cancer and breast cancer (as well as other pathologies including autoimmune neurologic diseases, blood disorders and conditions related to excessive apoptosis).
Smith et al [Cancer Research 66, 1917-1922, Feb. 15, 2006] teaches that down-regulation of CD24 using siRNAs in a panel of tumor cell lines (from common epithelial human cancers, including UM-UC-3 urothelial carcinoma cells, DU145 prostate carcinoma cells, HeLa cervical adenocarcinoma cells, MCF-7 breast adenocarcinoma, and SAOS-2 osteosarcoma cells) leads to a decrease in cellular proliferation.
U.S. Pat. Appl. 20040005596 teaches administration of siRNA molecules targeted to CD24 for the treatment of a variety of cancers.